1)After MIss Chan ran at speed of 2m/s for 30 seconds, Mr Lee set off to run at a speed of 3m/s at the same point. If we count from the set off time of Miss Chan, how long will it take for Mr.Lee to catch up with her?
2)Calvin and Wayne drive at a speed of 70km/h and 80km/h respectively. Calvin set off from point A and Wayne at point B. The distance between the two points is 150km. If they set off at the same time towards each other, when will they meet?
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2012-03-27 3:26 am
回答 (2)
2012-03-27 5:32 am
✔ 最佳答案
1) let t be the time required60 + 2t = 3t
t = 60s
Note that the time is count from set off time of Miss Chan
The time required should be 60 + 30 = 90s
2)let t be the time required
70t + 80t = 150
t = 1 hours
2012-03-27 4:27 am
It will take Mr Lee 20 seconds.
20 seconds x 2m/s ./. 3m/s = 20 seconds
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They will meet in an hour.
Distance a -B = 150 km ./. (70km +80km/hour) = 1 hour
20 seconds x 2m/s ./. 3m/s = 20 seconds
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They will meet in an hour.
Distance a -B = 150 km ./. (70km +80km/hour) = 1 hour
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